1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a method and device for removing a tubular blanket or tubular plate from a respective printing press cylinder.
2. Background Information
U.S. Pat. No. 5,429,048 to Gaffney et al. discloses an offset lithographic printing press in which a web of material to be printed passes through a series of print units. Each of the print units has a plate cylinder, a blanket cylinder and an impression cylinder, which may be a second blanket cylinder. A flat printing plate containing an image may be fastened to the plate cylinder. A gapless tubular-shaped blanket may be fastened to the blanket cylinder. A frame of the printing unit supports the plate and blanket cylinders. A portion of the frame adjacent one axial end of the blanket cylinder is moveable in order to provide an opening in the frame so as to provide access to one end of the blanket cylinder. The tubular printing blanket, which is replaceable, may be moved axially through the opening in the frame. U.S. Pat. No. 5,429,048 also discloses that the blanket cylinder interior has passages for communicating air to the outer peripheral surface of the blanket cylinder. Air pressure applied to the interior of the blanket cylinder is thus communicated to the interior of the blanket to expand the blanket as the blanket is inserted onto the blanket cylinder. After the blanket is placed over the blanket cylinder, the air pressure may be removed. The blanket then contracts around the blanket cylinder and tightly engages and grips the blanket cylinder. To remove the blanket, air pressure is again applied to enable the blanket to be manually moved off the blanket cylinder.
A problem with the above-mentioned printing press is that the inner surface of the blanket, or the outer surface of the blanket cylinder may become contaminated. For example, sticky substances such as printing inks inadvertently may become attached to the inner surface of the blanket. When an operator attempts to remove the blanket from the blanket cylinder by providing air pressure to the inner surface of the blanket and sliding the blanket off axially, the sticky substances may prevent easy removal. Likewise, manufacturing imperfections or environmental conditions such as humidity and temperature can cause the blanket to be difficult to remove.
U.S. Pat. No. 4,913,048 to Tittgemeyer discloses a printing press with a sleeve-shaped gapless printing form or plate which may contain an image. This sleeve-shaped printing form is axially removable over the plate cylinder. The sleeve-shaped printing form may be fastened to the plate cylinder by expanding the form with pressure from a pressure medium. The sleeve-shaped printing form is then moved manually over the plate cylinder and allowed to relax.
This type of printing press with axially removable printing forms may suffer from the same problems as that disclosed in U.S. Pat. No. 5,429,048.
An object of the present invention is to provide a device to aid in the axial removal of blankets or other types of printing sleeves. An additional or alternative object is to provide a method for axially removing blankets or other types of printing sleeves.
The present invention provides a printing sleeve removal device to aid in removing of a printing sleeve.
In one embodiment, the present invention provides a printing sleeve removal device having a first jaw arm and a second jaw arm pivotable with respect to the second jaw arm, the first and second jaw arms having ends forming a jaw to engage a printing sleeve.
Advantageously, the device may be insertable through an opening in the printing press so that an operator can use the device to remove the printing sleeve. This aids in quick and simple application of the device and permits an operator to remove a blanket or other type of printing sleeve.
The ends advantageously may be provided with gripping pads to aid in friction.
In one embodiment, the jaws may be tightened by moving two handles of the arm toward each other, the handles being on the jaw arms opposite the ends. This embodiment creates a simple and convenient mechanical sleeve removal device.
In another embodiment of the present device, the jaws may be tightened with the aid of a motor, preferably by rotating a toothed gear which forces the jaw shut.
The present invention is particularly applicable to axially removable blankets of the type described in U.S. Pat. Nos. 5,429,048 and 5,323,702, which are hereby incorporated by reference herein. The compressibility of the outer layer of the blanket provides a firm grip on the blanket for the device, without necessarily squeezing the innermost tube of the blanket, which could create disadvantageous friction between the innermost tube and the blanket cylinder. This friction could make removable of the blanket more difficult. It may be desirable to have the printing sleeve removal device clamp and pull on the sleeve as opposed to the rubber blanket on the sleeve in order to not damage the blanket surface or to get at a slightly smaller diameter.
Preferably, the jaw engages the outer surface of the printing sleeve. An alternative is to have the printing sleeve tube extend past the cylinder body end and have the jaw expand inside the tube to create the frictional force on the inside of the tube and then remove accordingly.
In another embodiment, the present invention provides a printing sleeve removal device operating on a gear side of the printing sleeve, the removal device including a clamp for engaging the gear side of the printing sleeve and an actuator connected to the clamp to move the clamp and the printing sleeve axially away from the gear side.
The present device also may be used with other types printing sleeves, such as the tubular printing forms described in U.S. Pat. No. 4,913,048, which is also hereby incorporated by reference herein.
In yet another embodiment, the present invention provides a printing sleeve removal device comprising at least one band for wrapping around at least part of a printing sleeve and a tightening device connected to at least one band for tightening at least one band.
Advantageously, at least one band of the printing sleeve removal device includes a first semicircular band and a second semicircular band. More than one band and/or tightening device can be included to provide balanced pulling force on the printing sleeve. This would in turn minimize any tendency to bind as the printing sleeve is removed. These bands may be connected at one end by the tightening device and at their other ends by a second tightening device, so that the removal device is in a circular shape which can be placed axially over the printing sleeve. This form aids in quick and simple application of the device and permits an operator to remove a blanket or other type of printing sleeve.
Each tightening device may comprise a first side plate and a second side plate, the two side plates supporting a first pin and a second pin. The pins preferably are non-rotatably fixed to the side plates, and one of the first pin and the second pin is attached to an actuating rod. One end of the first band is attached rotatably to the first pin and an end of the second band is attached rotatably to the second pin.
By twisting a handle on the actuating rod of at least one of the tightening devices, the tightening device twists so the effective diameter of the circle formed by the first and second semicircular bands is reduced. Preferably two tightening devices are actuated to reduce the effective diameter. As a result, when the removal device is placed over a printing sleeve and the tightening devices are actuated, the sleeve may be firmly grasped and axially removed.
The embodiments of the present invention form an effective way for removing printing sleeves. The sleeve may be grasped more firmly than by hand.
A lip or slightly larger diameter may be located on the end of the printing sleeve. This lip allows the sleeve removal device to reduce diameter and pull directly on the lip as opposed to relying on frictional clamping force.
The present invention also provides a method for axially removing a printing sleeve comprising placing a sleeve removal device over the printing sleeve, tightening the sleeve removal device so as to grasp the sleeve, and axially pulling on the removal device so as to axially remove the printing sleeve. This method provides a safe and effective way to remove printing sleeves.
Advantageously, the above method further includes providing air pressure to an inner surface of the printing sleeve. Moreover, the above method preferably is used with a sleeve which is a blanket in an offset printing unit. The tightening step then may include tightening the sleeve removal device so as to compress a compressible layer of the blanket. An inner tube of the sleeve thus advantageously may remain unaffected by the removal device.
The present device need not be used for every blanket removal. A press operator may first attempt to remove a blanket manually, and determine if the blanket sticks. If so, the operator utilizes the removal device. The present invention therefore also advantageously includes a method of axial removal of a printing sleeve comprising attempting to manually remove a printing sleeve axially, determining that the sleeve cannot be manually removed, placing a sleeve removal device over the printing sleeve, tightening the sleeve removal device so as to grasp the sleeve, and axially pulling on the removal device so as to axially remove the printing sleeve